The invention relates to a suspension system for a vehicle wheel suspension having a first spring element in the end clamped between the vehicle body and a vehicle wheel and a second or additional spring element which in the end can be clamped between the vehicle body and the vehicle wheel by the introduction of a force or of a momentum by a mechanical tensioning element, which spring element can thereby be connected parallel to the first spring element, while this additional spring element is not active without force or momentum introduced into the system, and furthermore having a pressure addition spring element which, in the case of large spring excursions of the first spring element, by way of an end stop, becomes active or is connected. In addition to German Patent Document DE 10 2004 013 559 B4, reference is made to German Patent Document DE 41 04 904 A1 as well as German Patent Document DE 33 23 026 A1 with respect to the known state of the art.
Chassis of motor vehicles can be designed according to different philosophies. Comfortably designed chassis of passenger cars are relatively soft; chassis of a sportier design are relatively hard. In addition to the different philosophy of the individual manufacturers of automobiles or passenger cars, in the case of some vehicles, a “sporty chassis” may be chosen as optional equipment. In order to design this selection in the respective vehicle in a variable fashion, some manufacturers offer so-called adjusting shock absorbers by which the driver can choose between a comfortable and a sporty shock absorber coordination. Although this different shock absorber adjustment has a subjective influence on the driver's feelings, objectively no improvement can be achieved with respective to a sportier vehicle handling when the damping is hard. An adjusting possibility of the spring rate(s) would be more favorable here.
The latter is basically known for vehicles; compare, for example, the second document mentioned above which, however, shows a relatively high-expenditure controllable suspension system for wheel suspension on motor vehicles. In contrast, a variable suspension system for a motor vehicle having at least one main spring element and at least one shock absorber described in the initially first-mentioned German Patent Document DE 10 2004 013 559 B4 is simpler. The main spring element consists of a bearing spring and as usual of a pressure addition spring as well as a tension stop spring. In addition, a second spring element is provided which counteracts or can counteract the main spring element and can be optionally activated for this purpose by way of an adjusting system, the engaged second spring element causing a spring rate intensification by a premature intervention of the pressure addition spring present in the compression direction and a lowering of the motor vehicle. According to this known state of the art, the pressure addition spring therefore always has to be in an engagement when an increased spring rate is desired. Since, however, a pressure addition spring is also used as an end stop for limiting the spring excursion of the bearing spring, the spring rate of the pressure addition spring is relatively high; that is, the amount of its spring rate is relatively large and this pressure addition spring is therefore relatively hard. However, if this pressure addition spring is always engaged when the vehicle is lowered, the chassis will be extremely hard and therefore uncomfortable.
By the present invention, a similar suspension system (as the one known from German Patent Document DE 10 2004 013 559 B4) now is to be indicated by which, however, a softer and therefore more comfortable chassis can be presented (=object of the invention). For a suspension system of a vehicle wheel suspension having a first spring element between the vehicle body and wheel and a second spring element, the solution of this task is characterized in that the introduction of the force or the momentum for activating the second or additional spring element does not activate the pressure addition spring element.
In principle, it is known that, when two or more spring elements act in parallel between two components, the effective total spring rate is composed of the sum of the partial spring rates. By connecting one or more additional spring elements to a first spring element, the effective total spring rate can therefore be varied. In a chassis or a wheel suspension of a vehicle, a second or additional spring element can therefore be connected in parallel to the usual bearing spring here called the first spring element—, in order to vary the hardness of the chassis. This is basically known and thus also implemented in the above-mentioned known state of the art. In the above-mentioned state of the art according to German Patent Document DE 10 2004 013 559 B4, the connectable second and additional spring element is the so-called pressure addition spring of that document which, in FIGS. 1a, 1b of that above-mentioned document, has the reference number 16, in connection with the second spring element counteracting the so-called bearing spring of that document which, in FIGS. 1a, 1b of that above-mentioned document, has the reference number 18.
However, with the present invention, it was recognized that it is not required to engage the pressure addition spring according to German Patent Document DE 10 2004 013 559 B4, which in the present invention is called as pressure addition spring element. On the contrary, for changing the spring rate, it is sufficient for only a second or additional spring element, which also exists in the above-mentioned German Patent Document DE 10 2004 013 559 B4, to be connected, that is, in the end, to be clamped between the vehicle wheel and the vehicle body, between which a first spring element constructed as a pressure spring is already clamped as the so-called bearing spring. In this case, the second spring element by no means has to act as a pressure spring but the second spring element can definitely also act as a tension spring which, by a mechanical tension device, is clamped between the vehicle wheel and the vehicle body.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.